Are Density-dependent Effects on Elasmobranch Maturity Possible?

Fecundity and size at first maturity of elasmobranchs are believed to be limited by body size, making density-dependent effects on these life history traits unlikely. To examine the potential for density-dependent effects on size at first maturity, female spiny dogfish ( Squalus acanthias) off the northeast coast of the United States were examined to determine both the presence of free embryos, fertilized eggs, or ovarian eggs, and the number of free embryos in each female in relation to maternal body size during 1998-2002. Severe biomass declines of the adult female portion of the population preceded and continued throughout the study period. Since the period of high abundance in the late- 1980s, size at first maturity has declined from 75 cm to 66 cm and the median size at maturity ( L50) has declined from 85 cm to 79 cm; however, the relationship between number of free embryos and maternal length has not changed.